Reentry rotary fluid pump



July 2, 1963 D. s. SANBORN ETAL 3,095,820

REENTRY ROTARY FLUID PUMP Filed Feb. 29, 1960 EN W 7 5 ml 5m NNM i n 5.L5 H M M United States Patent 3,095,820 REENTRY RDTARY FLUID PUMP DanielS. Sanborn, San Diego, and Joe L. Byrne, Gardena,

Califl, assignors to McCulloch Corporation, Los Angeles, Calif., acorporation of Wisconsin Filed Feb. 29, 1960, Ser. No. 11,514 9 Claims.(Cl. 103-96) Our invention relates to pumps generally known as dragpumps which include turbine, turbulence, regenerative, peripheral,traction, vortex, friction and reentry pumps.

Such pumps are usually a simple, single, impeller device with structuralfeatures similar to centrifugal pumps but with head-capacitycharacteristics approaching those of positive displacement pumps.

Our invention more particularly relates to a unique design of reentrypump in which high fluid heads may be produced at relatively lowperipheral velocities with a design of relatively simple mechanicalcomponents.

It is an object of our invention to provide a pump of the classdescribed in which secondary vortices and peripheral flow reversals arematerially reduced with the result that greater kinetic energy transferfrom impeller to fluid is attained.

It is another object of our invention to provide a pump of the classdescribed having the features referred to in the preceding paragraph inwhich the impeller is provided with straight canted vanes located insemicircular impeller passages.

It is a still further object of our invention to obtain a superior andmore eflicient flow pattern by employing a unique improved portingarrangement.

It is a still further object of our invention to provide a pump of theclass described in which superior pumping action is achieved by usingunique flow channel and impeller configurations which promote acentrifugal reentnant flow pattern.

In using such a pump in handling air or other compressible orincompressible fluids there are present in the pump inherent losses inthe pressure head developing ability of the pump. Such losses are due tothe throttling expansion of gases trapped in the impeller after thevanes have passed the barrier or sealing block of the structure whichseparates the pump outlet from the pump inlet.

Accordingly, it is 52111 object of the invention to provide a reentrypump of improved construction for handling air or other compressiblefluids which minimizes such inherent losses in the head developingability of the pump as those due to the throttling expansion of gasestrapped in the impeller after the impeller vanes have passed the sealingblock.

Another object is to provide superior inlet and exhaust porting whichincreases head and efficiency characteristics of the reentry pump of theinvention when handling either compressible or incompressible fluids.

Numerous other objects and additional advantages of the invention willbecome evident from the following detailed description and drawings ofpreferred forms of our invention.

FIG. 1 is a sectional elevational view of an embodiment of the reentrypump taken along a plane passing through its axis of rotation and asealing block;

' FIG. 2 is a partial cross-sectional view of the embodiment of FIG. 1taken along line 22 and showing the structure and arrangement of theimpeller vanes;

FIG. 3 is a view similar to that of FIG. 2 but taken along line 3-3 andshowing the inner surface of the casing of the pump;

FIG. 4 is a partial sectional view taken as along curved line 4-4 ofFIG. 2 showing additional structural and arrangement features of theimpeller vanes and the sealing block, and showing inlet, outlet and warmgas bleed ports;

FIG. 5 is a fragmentary view similar to that of FIG. 3 showing a sealingblock and port arrangement in another embodiment of the invention;

FIG. 6 is a partial side elev-ational view showing a pump of theinvention applied to a motor vehicle for use as a power absorber; and

FIG. 7 is a fragmentary cross-sectional view taken as along a line 7-7of FIG. 6, drawn to a greatly enlarged scale, and showing a detail of ashut off valve.

In FIGS. 1 to 4 inclusive, we have illustrated a preferred form of apump incorporating the features of our invention. Referring to thesefigures, the numeral 11 represents a pump casing which has mounting feet11a for securing it in an operating position. The casing 11 provides animpeller chamber 11b in which an impeller 13 is rotatably supported by ashaft 12 which is in turn mounted in ball bearings 12a of the casing 11.

The impeller 13 is symmetrically formed on opposite sides of a verticalcentral plane and near its periphery is provided with annularsemicircular impeller channels 15 in which vanes 14 are positioned. Thevanes 14 extend radially with respect to the axis of rotation of theimpeller 13 and are canted or inclined forwardly with respect to thedirection of rotation of the impeller 13, as illustrated best in FIG. 4.The acute angle of the vane 14 with respect to the central rotationalplane of the impeller 13, as indicated at 14a is between about 20 andabout 70 degrees, preferably between about 30 and about 60 degrees.Especially good results have been obtained when handling air in a pumpwherein the angle was between 40 and 50 degrees.

The walls forming the sides of the chamber 11b provide annularsemicircular flow passages 21 which are on the same diameter as theannular semicircular channels 15. The relationship between the channels15 and flow passages 21 are illustrated best in FIG. 1. Sealing surfaces17 and 18 are provided outwardly and inwardly respectively of channels15 and passages 21 to seal off the two sets of channels and the two flowpassages and to prevent leakage from the pump.

The casing 11 provides a sealing block 20 which delines the inlet endand the outlet end of the flow passages 21. Fluid to be pumped, whetherit be liquid or gas, enters the fluid passages 21 through inlet openings22 formed in the side walls 11c of the casing 11, and the fluid passesfrom the outlet ends of the passages 21 through outlets 23, as shownclearly in FIG. 4. The end of the sealing block 20 defining the outletend of the passages 21 has a surface disposed in each passage 21substantially in a radial plane passing through the axis of rotation ofthe impeller 13. The outlets 2.3 have openings 23a which are positionedentirely in said surfaces of the sealing block 20. Outlets 23communicate with diffusers 24. As best shown in FIG. 4, the angle of theoutlets 23 to the rotational plane of the impeller 13 is made so thatthe outlets are aligned with the direction of flow of fluid dischargingfrom the impeller vanes 14 of the impeller. Thus it can be understoodthat by positioning the opening of the outlet entirely within a surfacesubstantially normal to the direction of rotation of the impeller andpositioning the outlet at an angle substantially in alignment with theflow of fluid as it leaves the impeller vanes, a flow path out of thepump is obtained which is in accordance with that developed within thepump, and as a result shock losses are reduced materially with asubstantial increase in the efliciency of the pump. The throats of theoutlets 23 are followed by diffusers 24 of increasing cross-sectionalarea to give maximum efliciency to the conversion of kinetic topctential energy as the fluid discharges from the pump. The outlets 23,as best shown in FIG. 3, are positioned in the outer, circumferentialportion of the sealing block 20.

A feature of our invention resides in the use of warm gas bleed ports 25formed, as best shown in FIGS. 3 and 4, through sealing block 20, andcommunicating with flow passages 21. Ports 25 also are positioned in theouter, circumferential portion of sealing block 2%) and are sealed frominlet ports 22 to prevent mixing of warm bleed gas with inlet gas.

In the operation of a reentry pump of the type shown in FIGS. 1 to 4,the inlet fluid enters at inlet ports 22, is drawn into the impeller 13into channels 15 between vanes 14 near the roots or innercircumferential portions thereof. While under the eiiect of centrifugalforce, the fluid then continues in a substantially helical path be tweeneach pair of adjacent vanes 14 and into and out of flow passages 21 ofcasing ll. many times before it is discharged through outlet port 23.During the substantially helical traverses of the fluid mentioned abovethe static pressure gained in the semicircular channels 15 between apair of vanes 14- is consumed in the flow passages 21 in forcing thefluid radially inwardly through the region of the roots or innerportions of vanes 14 for reentry into the channels 15 of impeller I3.The kinetic energy gained by the fluid is converted into potentialenergy in the form of static pressure in the flow passages 21 of thecasing 11 by fluid deceleration. It isthis latter conversion of kineticenergy which is responsible for the head rise produced in the reentrypump of the invention.

When prior art reentry pumps are used to handle gases such as air, orother compressible fluids, they suitor an inherent decrease in headdeveloping ability. It is an important feature of the pump of ourinvention that this decrease in realizable pressures does not occur'tosuch an extent as in prior art pumps when handling air or other gases orcompressible fluids. We have discovered that this decrease in headdeveloping ability is partially due to the recirculation of warm airexhaust for example, which is trapped between impeller vanes 14 by thesealing block 29. This recirculated warm air, because of its heatcontent, is not as compressible as the cooler charge air, or other gas.decrease in the head developing ability or realizable pressures of thepump. 7

- We have found that a substantial improvement in head developingability is realized by using the warm air or .gas bleed ports 25described hereinabove. These ports purge the pump of the unavailabletrapped warm or hot compressed gas and prevent recirculation thereof. Inthis manner the inlet ports 22 constantly reprime the channels 15between adjacent vanes 14 with cool intake gas, which is most readilycompressed, immediately after the channels have been purged of trappedwarm :or hot recirculating compressed gas. Thus higher pressures aredeveloped and increased efficiencies result by the use of this featureof our invention when handling gases or compressible fluids.

The use of the straight canted vanes 14 in the pump of our invention hastwo important advantages over the structures used in prior art pumps.First, the kinetic energy transfer, from impeller vanes 14 to thecharge? fluid, is greatly increased, as in a conventional centrifugalpump utilizing an inducing inlet section and forward swept blade tips.Secondly, the use of straight canted vanes 14 materially reduces shocklosses that would be encountered by the charge fluid upon entering theirn peller 13.

It will 'be'un'derstood that'the reentry pump of our invention has manyvaried uses and applications in situa tions where it is desired totransfer gases or fluids including air, gaseous hydrocarbons, water,oil, gaseous or liquid chemicals, or fluid mixtures of gases andliquids.

Reentry pumps of our invention have becnused to supply Thus, thisrecirculated air causes a scavenge air for separately charged two-strokeengines, to supply air to turbosuperchargers, as liquid pumps, and fordrag turbines. Many additional miscellaneous uses tor the reentry pumpof our invention will present themselves to persons engaged in thevarious engineering fields.

In some applications, the warm or hot gas bleeds 25 are not required andcan be left out of the structure. In such cases the pump will resemblethe structure shown in FIG. 5, which is a view showing the sealing'block 2i region and the inlet port 22 and outlet port 23. The structureshown in FIG. 5 can conveniently be used in handling liquids or in caseswhere the entrapment of warm gases in the manner described hereinabove'is not a serious factor.

An example of an interesting application of the reentry pump of ourinvention, described above in connection with FIGS. 1 to 4, is shown inFIGS. 6 and 7, wherein the pump is used as a power absorber or retarder,indicated in the illustrated assembly at 30.

This retarder has the same basic internal structure as the reentry pump,shown in FIGS. 1-4 and has 'a generally typical circular casing 31. InFIG. 6, the casing 31 is shown to be secured against rotation to theframe or other parts of a truck 32. In this embodiment the drive shaft33 of the truck replaces the typical pump shaft 12 An additional set ofgears (not shown) can be added to the rctarder to increase its speedabove that of the drive shaft 33. The impeller, which may be identicalwith impeller 13 in FIGS. 1-4, is in continuous rotation when the driveshaft 33 is rotating and causing the truck to move. Also, aclutch (notshown) can be added to the retarder installation for engagement anddisengagement with the trucks drive shaft. When no retardation isdesired, the clutch is disengaged.

Theretarder 30 may have typical diflusers 34 from each side thereofequivalent to the difiusers 24 which are connected to the pumpdischarges 23. The diffusers 34' are shown to join in a common outlet 35on which is schematically attached the gate-type shut off valve 36,shown in detail in FIG. 7. This valve may be operated by flexible cable37 which terminates in the truck cabin at handle or knob 38. Inaddition, the retarder may be equipped with a 'vacuum pump (not shown)and an inlet shut oh valve to minimize energy absorption when notdesired. V

In operation, when the truck is moving in a normal way on level groundor going up an incline, the valve 36 is wide open so that no pressurebuilds up within the retarder 30. However, when the truck starts down anincline, the operator, to make use of the retarder, will close the valve36 the desired amount so as to hold back the movement of the truck[ Inthis embodiment, a hot air exhaust (not shown), similar to exhaust 25 inFIG; 4, may also be provided. Thus pump 11, shown in FIGS. 1-4 may beused as a reentry compressor to absorb the power caused by the weight ofthe truck going downhill by compressing atmospheric air,a noncaptivemedia, when the valve 36 is closed or partially closed. This, of course,will decrease the speed of the truck.

It has been found that 'a retarder, according to the present invention,will absorb higher horsepower rates for a given weight size than anyother system currently in use in this country or Europe. It alsoprovides surgetree power absorption at modest speeds due to the uniqueinherent characteristics of the reentry compressor. Test dataindicatesthat the'power absorption range can be easily 6m 1 at a specified speed.i I

"Such a retarder is extremely simple so as to have maximum reliability,2. low maintenance cost, a low initial cost and be relativelylightweight. Another advantage of the present retarder is that it isinherently an antiskid device because the power absorption is reduced bythe cube of the speed reduction. This, of course, is especiallyadvantageous when operating on roads. coated with ice.

A further advantage is that the basic capacity of the retarder is notlimited by the vehicles radiator capacity as are some retarders in theprior art since the heat energy is ejected directly to the atmosphericair.

It may be readily seen from the foregoing that the simple structureprovided in the reentry pump, according to the present invention, may beused with equal facility for pumping gases or liquids and may be used ina novel combination as a power absorber on heavy motor vehicles tothereby add considerable safety to the highways and increased revenue totruck operators.

We claim:

1. In a reentry rotary fluid pump: a casing; an impeller mounted forrotation in said casing; a plurality of spaced vanes disposed on saidimpeller at a common radius from the center of the rotational axis ofsaid impeller, said vanes extending outwardly from said impeller; a flowpassage in said casing laterally outwardly of said vanes and incommunication therewith; an inlet into said casing and into said flowpassage; a discharge passage from said flow passage outwardly throughsaid casing; a sealing block in said casing outwardly of said vanesproviding a seal between said inlet into said flow passage and saiddischarge from said flow passage; and a fluid bleed port adjacent thesealing block open through the casing to the vanes adjacent the outerportion of said flow passage for preventing recirculation of trappedfluid in the flow passage.

2. In a reentry rotary fluid pump: an annular-shaped casing; a circularimpeller mounted for rotation in said casing; a plurality ofcircumferentially spaced vanes ex tending outwardly from said impelleradjacent the circumference thereof; a substantially circumferential flowpassage in said casing and extending immediately laterally outwardly ofsaid vanes and being in communication therewith; a bucket formed betweeneach two of said vanes, the inner surface of said buckets extending between each of said vanes being complementary to the surface of said flowpassage outwardly therefrom so that when the impeller is rotated, fluidin said buckets will repeatedly circulate from the radially innerportion thereof in relation to the axis toward the radially outerportion thereof away from said axis and into the radially outer portionof said flow passage toward the radially inner portion of said flowpassage; a sealing block in said casing forming two ends of said flowpassage; a fluid inlet through said easing into said flow passageadjacent a side of said sealing block toward the direction of rotation;a fluid discharge on the other side of and through said sealing blockconnecting said flow passage and the exterior of said casing, said fluidinlet being in the radially inner portion of said flow passage to causefluid to enter the radially inner portion of said buckets on saidimpeller, said fluid discharge being in a radially outer portion of saidsealing block in alignment with the radially outer portions of said flowpassage and said vanes; and a warm gas exhaust extending outwardlythrough the sealing block adjacent the inlet side thereof and outwardlythrough said casing, said warm gas exhaust being in the radially outerportion of said sealing block and being radially outwardly of saidinlet.

3. In a reentry rotary fluid pump: a generally circular casing; acircular impeller mounted for rotation within said casing; a pluralityof circu-mferentially spaced vanes extending outwardly from saidimpeller adjacent the circumference thereof and from at least one sideof said impeller generally toward the direction of rotation and at anacute angle with the axis of rotation, each two of said vanes forming abucket in the space therebetween, each of said buckets having plane sidesurfaces formed by said vanes and having a generally semicircularoutwardly opening concave inner surface; a substantially annular flowpassage in said casing extending immediately laterally outwardly of saidvanes and being in communication therewith, said flow passage having agenerally semi:

circular cross section and opening inwardly toward said vanes so that aplane through said axis of rotation and through said flow passage andsaid impeller vanes will cut a generally circular cross section half ofwhich is formed by said flow passage and the other half of which isformed by said buckets between said vanes; a sealing block in saidcasing and forming two adjacent ends of said flow passage immediatelyoutwardly of said impeller vanes; an inlet into said flow passage fromthe exterior of said casing on the side of said sealing block toward thedirection of rotation and directed toward a portion of said vanes; adischarge outlet from said flow passage on the other side of saidsealing bloc-k through said sealing block and said casing, said inletbeing in the inner circumferential portion of said annular flow passageand said discharge outlet being in the outer circumferential portion ofsaid annular flow passage; and a warm gas exhaust extending outwardlythrough said sealing block adjacent the inlet side thereof and extendingoutwardly through said casing, said exhaust being in the radially outerportion of said sealing block and being radially outwardly of saidinlet, aportion of said inlet in said casing being advanced in thedirection of rotation relative to said warm gas exhaust.

4. In a reentry rotary fiuid pump: a generally circular casing; acircular impeller mounted for rotation within said casing; a pluralityof circumferentially spaced vanes extending outwardly from said impelleradjacent the circumference thereof and from at least one side of saidimpeller generally toward the direction of rotation and at an acuteangle with the axis of rotation, each two of said vanes forming a bucketin the space therebetween, each of said buckets having plane sidesurfaces formed by said vanes and having a generally semicircularoutwardly opening concave inner surface; a substantially annular flowpassage in said casing extending immediately laterally outwardly of saidvanes and being in communication therewith, said flow passage having agenerally semicircular cross section and opening inwardly toward saidvanes so that a plane through said axis of rotation and through saidflow passage and said impeller vanes will cut a generally circular crosssection half of which is formed by said flow passage and the other halfof which is formed by said buckets between said vanes; a sealing blockin said casing and forming two adjacent ends of said flow passageimmediately outwardly of said impeller vanes; an inlet into said flowpassage from the exterior of said casing on the side of said sealingblock toward .the direction of rotation and directed toward a portion ofsaid vanes; a discharge outlet from said flow passage on the other sideof said sealing block through said sealing block and said casing, saidinlet being in the inner circumferential portion of said annular flowpassage and said discharge outlet being in the outer circumferentialportion of said annular flow passage; and a warm gas exh-aust extendingoutwardly through said sealing block adjacent the inlet side thereof andextending outwardly through said casing, said exhaust being in theradially outer portion of said sealing block and being radiallyoutwardly of said inlet, the direction of said discharge into saidsealing block substantially following the direction of rotation of saidimpeller and the direction of the angles of said vanes.

5. For use as a retarder for a motor vehicle, a reentry rotary gas pumpcomprising: an annular-shaped casing; a circular impeller fitted forrotation in said casing and adapted to be mounted for rotation on thedrive shaft of a motor vehicle; a plurality of circumferentially spacedvanes extending outwardly from said impeller adjacent the circumferencethereof; a substantially circumferential gas flow passage in said casingand extending immediately laterally outwardly of said vanes and beingincommunication therewith; a bucket formed between each two of said vanes,the inner surface of said buckets extending between said vanes beingcomplementary to the surface of said flow passage outwardly therefrom sothat when the impeller is rotated, gas in said buckets will repeatedlycirculate from the radially inner portion thereof in relation to theimpeller axis toward the radially outer portion thereof away from saidaxis and into the radially outer portion of said flow passage toward theradially inner portion of said flow passage; a sealing block in saidcasing forming two ends of said flow passage; a gas inlet through saidcasing into said flow passage adjacent a side of said sealing blocktoward the direction of rotation; a gas discharge on the other side ofand through said sealing block connecting said flow passage and theexterior of said casing, said gas inlet being in the radially innerportion of said flow passage to cause gas to enter the radially innerportion of said buckets on said impeller, said gas discharge being in aradially outer portion of said sealing block in alignment with theradially outer portion of said flow passage and said vanes; and a warmgas exhaust extending laterally outwardly through said sealing blockadjacent the inlet side thereof and extending outwardly through saidcasing, said exhaust being in the radially outer portion of said sealingblock and being radially outwardly of said inlet.

6. For use as a retarder for a motor vehicle, a reentry rotary gas pumpcomprising: an annular-shaped casing; a circular impeller fitted forrotation in said casing and adapted to be mounted for rotation on thedrive shaft of a motor vehicle; a plurality of circumferentially spacedvanes extending outwardly from said impeller adjacent the circumferencethereof; a substantially circumferential gas flow passage in said casingand extending immediately laterally outwardly of said vanes and being incommunijcation therewith; a bucket formed between each two of saidvanes, the inner surface of said buckets extending between said vanesbeing complementary to the surface of said 'fiow passage outwardlytherefrom so that when the impeller is rotated, gas in said buckets willrepeatedly circulate from the radially inner portion thereof in relationto the impeller axis toward the radially outer portion thereof away fromsaid axis and intothe radially outer portion of said flow passage towardthe radially inner portion of said flow passage; a sealing block in saidcasing forming two ends of said flow passage; a gas inlet through saideasing into said flow passage adjacent a side of said sealing blocktoward the direction of rotation; a

gas discharge on the other side of and through said sealing blockconnecting said flow passage and the exterior of said casing, said gasinlet being in the radially inner portion of said flow passage to causegas to enter the radially inner portion of said buckets on saidimpeller, said gas discharge being in a radially outer portion of saidseal ing block in alignment with the radially outer portion of said flowpassage and said vanes; and a warm gas exhaust extending laterallyoutwardly through said sealing block adjacent the inlet side thereof andextending outwardly through said casing, said exhaust being in theradially ,outer portion of said sealing block and being radiallyoutwardly of said inlet, a portion of said inlet in said casing beingadvanced in the direction of rotation relative to said warm gas exhaust.

7. For use as a retarder for a motor vehicle, a reentry rotary gas pumpcomprising: a casing; an impeller fitted for rotation in said casing andadapted to be mounted for rotation'on the drive shaft of a motorvehicle; a plurality of spaced vanes disposedon said impeller at acommon radius from the center of the rotational axis of said impeller,said vanes extending outwardly from said impeller; a gas flow passage insaid casing laterally outwardly of said vanes and in communicationtherewith; a gas inlet into said casing and into said flow passage; agas discharge passage from said flow passage outwardly through saidcasing; a sealing block in said'casing outwardly of said vanes providinga seal between said inlet to said flow passage and said discharge fromsaid flow passage; and a gas bleed port adjacent the sealing block andopen through the casing to the vanes adjacent the outer portion of saidflow passage for preventing recirculation of trapped gas in the flowpassage.

8. In a reentry rotary fiuid pump: a generally circular casing; acircular impeller mounted for rotation within said casing; a pluralityof circumferentially spaced vanes extending outwardly from said impelleradjacent the circumference thereof from at least one side of saidimpeller generally toward the direction of rotation and at an acuteangle with the axis of rotation, each two of said vanes forming a bucketin the space therebetween, each of said buckets having plane sidesurfaces formed by said vanes and having a generally semicircularoutwardly opening concave inner surface; a substantially annular flowpassage in said casing extending immediately laterally outwardly of saidvanes and being in communication therewith, said flow passage having agenerally semicircular cross section and opening inwardly toward saidvanes so that a plane through said axis of rotation and through saidflow passage and said impeller vanes will cut a generally circular crosssection half of which is formed by said flow passage and the other halfof'which is formed by said buckets between said vanes; a sealing blockin said casing having opposite ends and forming two ends of said flowpassage immediately outwardly of said impeller vanes; an inlet into saidflow passage from the exterior of said casing adjacent the end of saidsealing block toward the direction of rotation and directed toward aportion of said vanes; and a discharge outlet from said flow passage insaid sealing block adjacent the other end of said sealing block; saidother end of said sealing block having a surface lying substantially ina radial plane through the rotational axis of said impeller, saiddischarge outlet having an opening disposed entirely in said surface,said discharge outlet extending from said opening outwardly through saidsealing block and said casing at an angle in the direction of rotationof said impeller, said inlet being in the inner circumferential portionof said annular flow passage and said discharge outlet being in theouter circumferential portion of said annular flow passage.

9. For use as a retard-er for a motor vehicle, a reentry rotary gas pumpcomprising: an annular-shaped casing; a circular impeller fitted forrotation in said casing and adapted to be mounted for rotation on thedrive shaft of a motor vehicle; a plurality of circumferentially spacedvanes extending outwardly from said impeller adjacent the circumferencethereof; a substantially circumferential gas flow passage in said casingand extending immediately laterally outwardly of said vanes and being incommunication there-with; a bucket formed between each two of saidvanes, the inner surface of said buckets extending between said vanesbeing complementary to the surface of said flow passage outwardlytherefrom so that when the impeller is rotated, gas in said buckets willrepeatedly circulate from the radially inner portion thereof in relationto the impeller axis toward the radially outer portion thereof away fromsaid axis and into the radially outer portion of said flow passagetoward the radially inner portion of said flow passage; a sealing blockin said casing having two opposite ends forming two ends of said flowpassage; a gas inlet through said easing into said flow passage adjacentone end of and on a side of said sealing block and a gas dischargeoutlet in said sealing block adjacent the other end of said sealingblock; said other end of said sealing block having a surface lyingsubstantially in a radial plane through the rotational axis of saidimpeller, said gas discharge outlet having an opening disposed entirelyin said surface, said gas discharge outlet extending from said openingoutwardly through said sealing block and said casing at an angle in thedirection of rotation of said impeller, said gas inlet being in theradially inner portion of said flow passage to cause gas to enter theradially inner portion of said buckets on said impeller, said gasdischarge outlet being in a radially outer portion of said sealing blockin alignment with the radially outer portion of said flow passage andsaid vanes.

References Cited in the file of this patent UNITED STATES PATENTS 5Burks Mar. 1, 1927 Bornemann Aug. 30, 1927 Burks Oct. 30, 1928 North eta1 June 27, 1933 De La Mater Apr. 5, 1938 10 10 McMillan Apr. 5, 1938Edwards et a1 Mar. 12, 1946 Cline a Apr. 14, 1953 FOREIGN PATENTS ItalyDec. 29, 1948 Germany Oct. 13, 1952 Germany May 11, 1953 France Jan. 22,1945 France Oct. 30, 1951

1. IN A REENTRY ROTARY FLUID PUMP; A CASING; AN IMPELLER MOUNTED FORROTATIONG IN SAID CASING; A PLURALITY OF SPACED VANES DISPOSED ON SAIDIMPELLER AT A COMMON RADIUS FROM THE CENTER OF THE ROTATIONAL AXIS OFSAID IMPELLER, SAID VANES EXTENDING OUTWARDLY FROM SAID IMPELLER; A FLOWPASSAGE IN SAID CASING LATERALLY OUTWARDLY OF SAID VANES AND INCOMMUNICATION THEREWITH; AN INLET INTO SAID CASING AND INTO SAID FLOWPASSAGE; A DISCHARGE PASSAGE FROM SAID FLOW PASSAGE OUTWARDLY THROUGHSAID CASING; A SEALING BLOCK IN SAID CASING OUTWARDLY OF SAID VANESPROVIDING A SEAL BETWEEN SAID INLET INTO SAID FLOW PASSAGE AND SAIDDISCHARGE FROM SAID FLOW PASSAGE; AND A FLUID BLEED PORT ADJACENT THESEALING BLOCK OPEN THROUGH THE CASING TO THE VANES ADJACENT THE OUTERPORTION OF SAID FLOW PASSAGE FOR PREVENTING RECIRCULATION OF TRAPPEDFLUID IN THE FLOW PASSAGE.